Anyone else running a Victron MultiPlus on a narrowboat and finding the shore power detection is absolutely baffling?

Mine's a MultiPlus-II 24/3000 and it keeps throwing a "no mains" fault even when I'm plugged into a perfectly decent marina 16A hookup — tested the socket with a kettle, works fine, so it's not the pedestal being awkward.

I've checked the input voltage limits in VictronConnect and they're set to 180–265V, which should be well within UK spec. Wondered if it's a frequency issue — some of these older marina pedestals apparently wander a bit — but I can't see an obvious frequency tolerance setting I'm missing.

Has anyone had to tweak the weak AC settings or mess about with the UPS function to get stable behaviour on dodgy marina supplies?

Jim1980 | Posts: 847

@AmyChapman89 Classic one this! Check your input voltage range settings in VEConfigure — the MultiPlus-II is quite fussy out of the box. Marina hookups can sag below the default lower threshold (184V I think) especially when neighbouring boats are drawing heavily. Kettle test won't catch that because it's a different load at a different time.

Try widening the AC input low voltage setting to around 180V and see if that helps. Also worth checking the input frequency tolerance — some older marina supplies wobble a bit on Hz too.

Grab a cheap plug-in voltmeter and leave it in the socket for a bit to log what's actually happening rather than just a snapshot reading. You might be surprised what you find.

What firmware version are you running on the MultiPlus?

GillWard | Posts: 312

@AmyChapman89 Worth also checking the input current limiter in VEConfigure — some marina hookups have slightly wobbly frequency (outside the 45-65Hz window the MultiPlus expects) rather than a voltage issue. Also had this exact problem on our boat last summer and it turned out the shore power lead itself had a dodgy neutral connection. Kettle still worked fine because it's less fussy, but the MultiPlus was seeing enough of a fault to reject it entirely. Swapped the lead and sorted immediately. Have you tried a different hookup point on the same marina? Sometimes it's just one pedestal with a grumpy earth. What cable are you using between the pedestal and the boat?

GeorgeShaw | Posts: 1,203

@AmyChapman89 Had almost identical grief on my boat last summer. One thing neither @Jim1980 nor @GillWard have mentioned yet — check your AC input cable itself, specifically the connections at the shore power inlet socket on the hull. On narrowboats these take an absolute battering from condensation and vibration, and a slightly corroded or loose connection can cause enough voltage drop under load that the MultiPlus decides the supply isn't stable enough to accept. It'll look fine on a multimeter with nothing drawing current, but the unit sees something different when it tries to actually sync. Give the connections a proper inspection and clean if needed. Also worth checking whether the fault only appears when the inverter side is loaded — that can point to an earthing issue rather than the input detection itself. What firmware version are you running?

WillWilliams | Posts: 456

@AmyChapman89 One thing worth adding to what @GeorgeShaw and the others have mentioned — marina shore power can have quite poor waveform quality, and the MultiPlus-II is surprisingly fussy about this. If the marina's supply has significant harmonic distortion or the frequency wanders even slightly outside tolerance, it'll reject it entirely.

Try logging the AC input data in VRM portal if you've got it connected — you'll often catch the fault happening in real time and see exactly what the voltage or frequency was doing at that moment. Narrows it down considerably rather than just guessing. Also worth checking whether the fault coincides with neighbouring boats running heavy loads like washing machines — that can pull the marina ring down enough to trip your unit momentarily. Simple thing but easy to miss.

WonkyWelder | Posts: 87

@AmyChapman89 One thing nobody's mentioned yet — check the AC input wiring at the back of the unit itself. I had a very similar fault on my cabin backup setup and it turned out the neutral had a dodgy crimp at the MultiPlus terminal. Looked totally fine visually but was giving just enough resistance to confuse the mains detection.

Tightened everything up with a proper torque screwdriver (Victron spec is in the manual) and it sorted it instantly.

Marina shore power can also be quite noisy — worth checking the input voltage and frequency logs in the VRM portal if you've got it connected. Sometimes the frequency wanders enough to trigger a fault even when the socket itself seems fine with a kettle.

HazelHermit | Posts: 312

@AmyChapman89 One thing I'd add that nobody's touched on yet — check your AC input current limit setting in VEConfigure or the VictronConnect app. On narrowboats especially, folk sometimes set it very low (6A or even less) to protect a dodgy marina supply, and if the MultiPlus senses the actual incoming waveform doesn't match its expectations at that threshold, it can get confused and throw spurious "no mains" faults rather than just limiting draw.

Also worth confirming the UPS function isn't interfering with detection sensitivity. Some boats have it enabled unnecessarily.

What firmware version are you running? There were some known quirks around mains detection on earlier 2.x builds that Victron quietly patched. If you're not on the latest, that alone might sort you. Check the Victron community forum too — there's a dedicated narrowboat thread with some cracking troubleshooting flowcharts. 🛶

BoatMark | Posts: 1,247

Mine did exactly this for three weeks before I discovered the marina's neutral-earth bond was absolutely cooked — Victron's being clever and protective whilst you think it's being stupid, classic British passive-aggression in circuit board form. Grab the VictronConnect app and check the AC input voltage readings live while plugged in; if it's reading anything below ~207V or showing wildly fluctuating numbers, the problem's upstream of your MultiPlus entirely and no amount of fiddling with your own wiring will fix it. Some marina hookups are genuinely embarrassing.

SparkyHiker | Posts: 43

Has anyone checked the input voltage range settings in VE.Configure? My MultiPlus was rejecting perfectly good shore power because the default lower threshold was set quite conservatively — some marina hookups do sag a bit under load and it was dropping below the acceptance window.

You can widen the AC input voltage range in the settings. Worth connecting via VictronConnect or a MK3-USB interface and logging what voltage it's actually seeing when it throws the fault — might tell you immediately whether it's a marginal voltage issue rather than a wiring problem.

DodgyDrifter | Posts: 89

@SparkyHiker makes a good point on the voltage range. Also worth checking your AC input current limit in VE.Configure — if it's set too low the unit can behave weirdly on marginal marina supplies.

One thing I'd throw in: dodgy shore power leads cause this more than people realise. Had a 16A lead with a slightly loose blue plug that was dropping out intermittently. Looked fine visually but the connection was marginal enough to confuse the MultiPlus.

Swap the lead first, it's the quickest free fix before diving into settings.